The long-term goal of this project is to develop a new strategy for manipulating the immune system of a tumor-bearing host to produce an effective tumor-specific response. This strategy is based on the following three principles: 1. Hapten-help is the augmentation of the immune response to an antigen by challenging, with the antigen conjugated to a hapten, an individual previously sensitized to the hapten. For tumor immunotherapy, methods will be developed for the neoantigenization of tumor cells and for the conjugation of haptens to purified tumor specific antigen. Hapten priming for help is expected to expand a clone of hapten-specific T cells, not only capable of helping B cells produce cytotoxic antibody for complement-dependent lysis, but also of inducing other tumor-specific effector mechanisms, such as T cell-mediated lysis and antibody-dependent K cell-mediated lysis. All three effector mechanisms will be studied in this project by standard in vitro techniques. 2. Hapten priming is also expected to generate a population of hapten-specific suppressor cells. As these would suppress tumor-specific effector mechanisms, suppressor-inactivation will be accomplished by pretreatment with the hapten conjugated to a nonimmunogenic carrier, such as D-GL. 3. Ir genes determining the ability of inbred strains of mice to produce hapten help and suppressor inactivation will be investigated. The information thus obtained should be useful in the selection of a hapten suitable for the immunoprophylaxis and immunotherapy of tumor-bearing mice of each strain.